Convert Environment Variable To Script Arguments

Question

I am trying to provide a configuration layer to my users by allowing them to specify an environment variable with command line options. This config is actually for a wrapper program (run.sh) which receives the arguments and then invokes my program (program.sh).

I am having a problem with the arguments maintaining their quotations, which causes unexpected arguments to be passed through.

Here is an example implementation:

run.sh

exec `pwd`/program.sh ${CONFIG} "$@"

program.sh

for var in "$@"
do
    echo "$var"
done

An example invocation would look like this:

$> CONFIG='--foo="bar baz quo" --foo2="bar2 baz2"' ./run.sh hello abc123    
--foo="bar
baz
quo"
--foo2="bar2
baz2"
hello
abc123

I would have expected output like:

--foo="bar baz quo"
--foo2="bar2 baz2"
hello
abc123

I have tried wrapping ${CONFIG} in run.sh in qoutes, but that just makes a single argument of --foo="bar baz quo" --foo2="bar2 baz2". Escaping the quotations inside of CONFIG also yields an incorrect result.

The environment is not the right way to pass arguments like this. — chepner
– chepner, Commented Mar 28, 2016 at 17:04
@cdarke the abc123 got put on the wrong line, updating the question to reflect that. — Lull3rSkat3r
– Lull3rSkat3r, Commented Mar 28, 2016 at 17:20
You can't do this safely. This is a problem with system init scripts as well and has been for ages. The only way to pass space-safe arguments is with an array which you can't export but could pass by name in some contexts. — Etan Reisner
– Etan Reisner, Commented Mar 28, 2016 at 18:44

cdarke · Accepted Answer · 2016-03-28 16:50:09Z

3

run.sh

eval exec `pwd`/program.sh "${CONFIG}" "$@"

program.sh

for var                     # The 'in "$@"' is not required, it is the default
do
    echo "$var"
done

Output:

$ CONFIG='--foo="bar baz quo" --foo2="bar2 baz2"' ./run.sh hello 
--foo=bar baz quo
--foo2=bar2 baz2
hello

Note sure where the abc123 in your output is supposed to come from.

answered Mar 28, 2016 at 16:50

cdarke

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1 Comment

anubhava Over a year ago

This is risky as CONFIG variable is coming from external users. Once can set CONFIG='$(rm program.sh); --foo="bar baz quo" --foo2="bar2 baz2"'

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